Tools: fix Cygwin CI build

There are currently issues where the non-.exe-suffixed files can't be
copied into the `artifacts` folder; `cp` claims "File exists".
Previously this worked but the suffix was added by Cygwin so all files
in `artifacts` had a `.exe` suffix anyway.

This is evidently intended, though non-intuitive, behavior:
https://sourceware.org/legacy-ml/cygwin/2009-08/msg00293.html

> On Cygwin, you should avoid having a file "foo" and a file "foo.exe"
> in the same directory at all cost to avoid puzzeling POSIX borderline
> behaviour like this.  What you do is essentially in the "not
> supported" class of problems.

> [...] Cygwin does not check for a file "foo", if the name of the file
> is explicitely given as "foo.exe".

Apparently something similar was addressed in PR #20926; the current
code installs files with both suffixes, but that fix contradicts the
info above and now has broken.

This PR changes the code to only install .exe-suffixed files, as opposed
to only non-.exe-suffixed files, which was the behavior before that PR.

Tools/scripts/cygwin_build.sh

@@ -33,20 +33,13 @@ WAF_OPTIONS="-j8"
     python ./waf sub $WAF_OPTIONS 2>&1
 ) | tee artifacts/build.txt
 
-# copy both with exe and without to cope with differences
-# between windows versions in CI
+# artifacts are expected to have .exe as they are executable
 cp -v build/sitl/bin/arduplane artifacts/ArduPlane.elf.exe
 cp -v build/sitl/bin/arducopter artifacts/ArduCopter.elf.exe
 cp -v build/sitl/bin/arducopter-heli artifacts/ArduHeli.elf.exe
 cp -v build/sitl/bin/ardurover artifacts/ArduRover.elf.exe
 cp -v build/sitl/bin/ardusub artifacts/ArduSub.elf.exe
 
-cp -v build/sitl/bin/arduplane artifacts/ArduPlane.elf
-cp -v build/sitl/bin/arducopter artifacts/ArduCopter.elf
-cp -v build/sitl/bin/arducopter-heli artifacts/ArduHeli.elf
-cp -v build/sitl/bin/ardurover artifacts/ArduRover.elf
-cp -v build/sitl/bin/ardusub artifacts/ArduSub.elf
-
 # Find all cyg*.dll files returned by cygcheck for each exe in artifacts
 # and copy them over
 for exe in artifacts/*.exe; do